Telephone-exchange system



April 8, 1930.

R. L, STOKELY TELEPHONE EXCHANGE SYSTEM Filed Au .'4, 1927 2 Sheets- Sheet 1 /NVENTOR.'

' HAY L. STOKE-L 5W A270 NE) Eatented Apr. 8, 1930 STATES RAY L. STOKELY, OF FLORAL PARK, NEW YORK, ASSIGNOR TO BELL TELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK TELEPHONE-EXCHANGE SYSTEM Application filed August 4, 1927. Serial No. 210,535.

a This invention 1 relates v to telephone. exchange systems and more particularly to improvements in party tion. V 5 In accordance with the invention each station on a four-party line is equipped with a relay, two of these relays being connectedto opposite sides of the line and designed to respond to high potential current of one polars ity applied from the central oflice, the other two also being connected to opposite sides and responsive to high potential current of the other polarity. Any relay in operating applies direct ground to the side opposite to which its winding is connected to operate a marginal test relay at the central office.

' The drawing, comprising Figs. land'2, illustrates the operation of an automatic telephone system embodying the invention. Fig.

1 shows a four-party line terminatingin a line finder. Fig. 2 shows a selector switch schematically and a trunk leading fromthe line finder switch including the message register control circuits.

The line finder F is of the :200-point step by step type having a vertical and rotary magnet and may be in general the same as that disclosed inthe patent to Carpenter, 1,567,240,'granted December 29, 1925. The

selector switch S is also of the two movement step by step type.

line message registra- The substations are equipped respectively with relays 105, 106, 107 and 108 and space discharge tubes 109,110, 111 and 112. The relay 105 and discharge device 109 are connected in series to a contact of the switchhook. When the switchhook is shifted a circuit is closed for relay 105 through the transmitter to the ring conductor of the line 100. A parallel path extends through the back contact of relay 105 to the tip conductor. The discharge tube 109 consists of two elements so arranged that when potential of sufficient value is applied in the proper direction current will flow, whereas if the potential is applied in the opposite direction substantiallyno current will flow. It will be assumed that the device 109 is so arranged that when current of negative polarity is applied to the line 100 current flows and the relay operates. r

The relay 106 and the discharge device 1 10 at the substation 102 are similarly connected to the switchhook, but in this case the switchhook when, shifted connects the relay and device directly to the tip side of the line,.the

path through the back contact of the relay leading to the ringside. The device 110 also permits current to flow when potential [ofco ne ative polarity is applied to the line.

'11: like manner the other substations 103 and 104 are equipped each with a relay and discharge device. The device 111, however, permits current to pass -when a source of-posi-. tive polarity is applied to the line "and the same is true of the device '112. V

For the purpose of a detailed description assume thatthe subscriber at substation 101 initiates a call. The initiation of the call 'zc causes the operation of line relay 113 in ir cuit from battery, through the right winding of said relay, back contact of relay114, ring conductor of line-100, through the talking transmitter and switchhook contacts, back ,75 contact of relay 105, tip conductor of the line, contact of relay 114 to ground throughthe left winding of relay 113. The p'otentialfof the operating battery atthe central ofiiceis not suflicient to cause current to flow through the space discharge devices of the substations. Relay 113 operates and applies battery potential through the winding of relay 114 and message register .118 in parallel contact ofrelay 113 totest terminal 137 in the ,35 bank of terminals 120. The register 118 does not operate in this circuit. Relay 113 also closes an obvious operating circuit for the group, relay 138. Relay 138, closes the start wire 139 from ground through the contact of the relay, thence over conductor 139, nor- 8 mal contacts of relay 131, normal contacts of the spring combination 128, winding of slow release relay 130 to battery.

Relay 130 closes a circuit from battery through the outer left contact of relay 131, i right winding of relay 132, contact of the rotary magnet 135, contact of the vertical magnet 136 to ground at the contact of relay 130. Relay 132. operates and closes a circuit from battery through the contact of relay 131, Winding of the vertical magnet 136, outer right contact of relay 133, contact of relay 132 to ground at the contact of relay 13 The magnet 136 operates, stepping the brushes 122, 123 and 124 up one step and opening the circuit of relay 132. Relay 132 releases, in turn opening the circuit of th magnet which on releasing recloses the cirthrough the contactof relay 138, segment .operates. 7 battery through the contact of relay 131, ,wlnding of the magnet 136,r1ghtw1nd1ng and 140, brush 126, leftwinding orrelay 133, contact of magnet 135, right winding of re lay 132 to battery at the contact of relay 131. Relay 132 remains energized to prevent further stepping of the switch and relay 133 Relay 133 locks in a circuit from contact of relay 133 to ground at the contact of relay 13 .0. I

; WVhen relay 133 operates, a circuit is closed. from battery through the winding of the rotary magnet 135, contact of relay 133, contact of relay 132 to ground at the contact of relay 130. The magnet 135 rotates the crushes onto the first set of terminals in the selected level. Magnet 135 opens the circuit'of relay 132, which releases, in turn opening the circuit of the magnet 135. The magnet 135 continues to step the brushes until the calling line 100 reached. 1V hen the brushes reach the terminals of the calling line a circuit is completed from battery over the test terminal 137, as above explained, upper brush 123, upper winding of relay 127, back contact of relay 131, left winding of relay 132 .to ground at the contact of relay 130.. Relay'132 remains energized to prevent further stepping by the magnet 135; Relay 127 also operates, closing a locking circuit from battery through its lower winding and contact, contact of magnet 135 to ground through the contact of relay 130.

Relay127 in operating closes a circuit from battery through the left winding of relay 131, front contact of relay 127 to ground at the closed contacts of the vertical off-normal spring combination 129. Relay 131 in operating closes a new holding circuit for relay 127, traceable from battery through the lower winding and contact of the latter relay, frcnt contact of relay 131 to the grounded sleeve conductor 142. Relay 131 also opens the energizing circuit of relays 132 and 133. and opens the holding circuit of relay 133. 7 Relay 131 also opens the circuit of slow-release relay 130. Before relay 130 can release to remove ground from conductor 142, a substitute ground is placed upon said conductor from the selector switch S in the well-known manner. Relay 127 in operating also extends the tip and ring conductors of the subscribers line 100 through to the circuits shown in Fig. 2.

During the time the line finder F is finding the calling line, the circuits shown in 2 are functioning preparatory to making a test to determine which one of the four substations initiated the call. At the time ground potential is applied to the sleeve conductor 142, slow-release relay 200 operates. The circuit for relay 200 may be traced from battery through its winding, outer right back contact of relay 131 to the grounded conductor 142. Relay 200 closes a bridge across the tip and ring conductors of the trunk 225 to prepare the selector switch S for operation This bridge includes the resistance Relay 200 also closes an obvious circuit for slow-release relay 201. Relay 201 in turn completes a circuit from battery through the winding of slow-release relay 207, contact of relay 201, back contacts of relays 206 and 204, to the grounded conductor 142. Relay 207 energizes and operates the relay 202 in a circuit from battery through the winding of the latter relay, contact of relay 207, thence through contacts of the relays 206 and 204 to the grounded conductor 142. Relay 201 in operating opens the bridge 226. but closes a substitute bridge through the resistance 227. Relay 202 in operating subsequently closes a substitute bridge 228. Thus the impulse relay at the selector S is held operated.

The relay 200 extends the tip and ring conductors of the connection leading from the line finder F to the marginal test relays 204 and 206, the windings of which are connected to the sources of high potential negative current 220 and 221. As soon as the line finder F finds the line 100 and relay 127 operates, a test circuit is completed from negative battery 221 to the lamp 211, left winding of relay 206, front contact of relay 200, thence over the tip side of the line, back contact of relay 105 through the switchhook contacts to the device 109 and relay 105 to ground. Another circuit is closed from negative battery 220, lamp 210, right winding of relay 204, front contact of relay 200, over the ring side of the line through the transmitter and switchhock contact to device 109, relay 105 and ground. The polarity of the device 109 is such that current is permitted to flow through both of these test circuits. The resistance of the test circuits, however, is such that neither of the marginal relays206 and 204 operates. Since current flows in the test ircuits relay105 operates and in operating opens the test circuit leading over the tip side of the line. The relay 105 at its front contact places a direct ground potential on the tip side of the line permitting the mar ginal relay 206 to operate. Relay 206 immediately locks in a circuit from battery through its right winding and front contact, conductor 229, front Contact of relay 131, to ground on conductor 142. Relay 206 opens the circuit of relay 207 which after an interval releases, releasing the relay 202.

This test has taken place during the releasing time of the slow relay 200. Relay 200 releases presently and opens the circuit of relay 201. Before relay 201 releases, however, the tipand ring conductors of the line are connected to ground through the resistance 230. This is forthe purpose of discharging the line before a high potential of opposite polarity is applied thereto. As soon as relay 201 releases the tip and ring conductors of the calling line are extended through the windings of the polarized relay- 203 to the selector switch S.

At the time the switch S is first seized it places a ground potential on thesleeve conductor 231 in the well-knownmanner. The conductor 231 extends through the normal contact of relay 212 to the sleeve conductor 142. This ground potential'is applied to the conductor 142 to hold the'finder F after the relay 130 releases. The slow-release'relay 215 also operates in a circuit from battery through its winding and back contact of relay 209 to the grounded conductor 231. The cut-off relay 114 is also energized at this time in a circuit from battery through its winding, contact of theline relay 113, upper brush 123, contact of relay 127 front contact of relay 131 to the grounded conductor 142. Relay- 114 operates and locks through its outer right contact and releases the line relay 113';

As above explained the relay 105 at the sub station 1101 in operating opens the test circuit leading through its back contact to the tip side of the line. The relay 105 remains energized over the ring side of the line as long asrelay 200 is operated. As soon as relay 200 releases, however, the circuit of'relay 105 is opened and the latter relay deene'r gizes completing the talking circuit;

As soon as thecalled subscriber answers polarized relay 203 is operated: in the usual manner and closes an obvious circuit for relay 209. Relay 209 completes a circuit from ground through the left ccntact'of relay 215, left contact of relay 209, winding of relay 208 to battery. Relay 208 operates and connects the positive pole of booster battery through its front contact, thence over conductor 232, inner left contact of relay 206, outer left contact of relay 204, conductor 233, contact of relay 127, upper brush 124, through the message register 115 to the opposite pole of battery and ground. The register 115 operates to charge the call to the substation 101.

, Relay 209 in operating opens thecircuit of relay 215 Whichafter an interval releases. Relay 215 opens the circuit of relay 208 which opensthe circuit to the message regise ter. Relay 215 on releasing closes a locklng circuit for relay 209, including the inner right front contact of relay 209, back contact of relay 215, outer front contact of relay 209 to the grounded conductor 231. Relay 209,v remains energized to prevent the reoperation of relay 215.

If the call originates at substation 102, then the relay 106 in operating places a direct groundpotential on the ring side of the, line which causes the operation of the marginal relay 204. Relay 204 looks directly to the sleeve conductor 142 and prepares an operating circuit for the individual messageregiser 116. 3 8

If the call originates at the substation 103, then neither of the relays 204 and, 206 oper: ates on the first test and consequently relay 20'; remains energized until after relay 200 releases. After relay 200; releases the relay 201 retracts its armalturesand extends the tip and ring conductors of the line through the front contacts of relay 202 tothe windings of relays 212 and 213 connected to. the positive pole of high potential batteris 218 and 219... Since the call originated at substation 103 the relay 107 operates and places'a ground potential on the tip side of the line causing the operation of the marginal relay 213. Relay 213 locks to the conductor 229 and prepares a circuit for the operation of message register 117 Should the call orlglnate at substation 104 the relay 108 would place ground potential on thering side ofv the line operating the relay 212. Relay 212 prepares'an operating circuit for the message register 118. This circuit leads over the sleeve conductor 142.

When relay 208 operates itopens the sleeve,

connection extending from conductor 231 through the normal contact of relay 208, right front contact of relay 212 to conductor 142. However, it substitutes the booster battery for the normal ground connection'on 'conductor 231. This prevents the release of the finder F.

lVhen conversation is finished ground potential is removed from conductor 231 causing the release ofrelay 127 and the cut-off relay 114. Relay 127 completes a circuit from battery through the Winding of release magnet 134, closed contacts 129, left contact of relay 133, back contact of relay 127, back contact of elay 130 to ground at the contacts 129. Magnet 134 releases the finder F toits normal position. M I

In case a. call is originated by the presence of an accidental ground connection on one or the other of the line conductors" or in case the subscriber attempts to simulate a calling condition at another substation in order to avoid the charge the relays204, 206, 2 12. and 213 operate in: combinations other than those in which they would normally function. Suppose the subscriber at substa tion 101 places a: ground connection on the ring conductor of. the line. When the receiver isremove'd the test circuits are closed as above explained. but since a ground potential: exists on the ringside of the line the relay 105 is short-circuited. Since the relay 105 does not operate the ground connection is-ext'ended through the switch contacts and the-:back contact ofsaidi relay to the tip side ofthe line. Thiscauses the operation of bo'threlays 204 and 206 at the central oiiice. Relay 204 in operating completes a circuit from battery through the winding of relay 214, contact of relay 204 to the grounded conductor 142. A circuit is now closed from ground through the contact of relay 206, front contact of relay 214 to the alarm device 235'. The alarm 235 indicates that an.

unstandard condition exists on the subscribers line. With both relays 204 and 206 operated no circuit is closed for the operation of the message register.

Suppose that one of the subscribers disconnects the front contact of the relay at his substation. This will prevent any one of the test relays 204, 206, 212 and 213 from opera-ting; Accordingly a circuit is closed from the grounded conductor 229 through the lower back contact of relay 202, back contacts of relays 206 and 213, back contact of reiay 214 to the alarm device 235. Since none of the test relays is operated the message register circuit is not closed.

WVhat is claimed is:

1. In a telephone system, a party line, relays, one at each of two substations, said relays being responsive to current of opposite polarity, operating circuits for said relays, the operating circuit of one relay including one side of the line and the operating circuit of the other relay including the other side of the line, and circuits closed by said relays in operating for applying potential to the side of the line opposite the side over which the relayis operated.

2. In combination, a line having a plurality of subscribers stations, a relay at one substation responsive to test current oi a given polarity, means controlled by the switchhook for connecting the winding of said relay to one side'of the line, a relay-at a second substation responsive to test current of the other polarity, means controlled by he substation switchhook for connecting said latter relay to the opposite side of the line, and circuits closed by said relays in operating for applying potential to the opposite side of the line to which the relay winding is conn ectible.

3.. In combination, a line having a plurality of subscribers stations, relays, one at each substation, a plurality of said relays. responsive to current of a given polarity, another plurality of the relays responsive to current of the opposite polarity, means controlled by the switchhooks at certain substations for connecting the windings of the corresponding relays to one side of the line, means controlled by the swit'chhooks at other substations for connecting the relay windings to the opposite side of the line, and a circuit closed through contacts of any relay for connecting ground to the side of the line opposite the side to which the relay winding is connectible.

4. In a telephonesystem, a line having a plurality of subscribers substations, relays, one at each substation, means controlled by the switchhook at each of two substations for connecting the relay windings to both tip and ring conductors of the line, means controlled by said relays for disconnecting their windings, one from the tip and the other from the ring conductors, and means controlled by either relay for applying potential to the line conductor opposite the one to which the relay winding remains connected.

5. In a telephone system, a central ohice, a line havingtwo substations, relays, one at each substation, means controlled by the switchhook at each substation for connecting the winding of the associated relay over two paths, one leading to the tip and the other to the ring conductors of said line, means for operating one relay to open the path to the tip conductor and for operating the other relay to open the path to the ring conductor,

means controlled by each relay for closing a circuit to the side of the line opposite the side to which the relay-winding remains connected, and message registers at the central ofiice controlled by said circuits.

6. In a telephone system, a central office, a line having two substations thereon, relays, one at each substation, an operating circuit for one relay including the tip conductor of the line, an operating circuit for the other relay including the ring conductor of the line, sources of potential of opposite polarity and test relays at the central ofiice, means for connecting said sources and said test relays to the tip and ring conductors of the line, said relays at the substations responsive to current of opposite polarity, means controlled by the relays at the substations in operating for closing operating circuits for said test relays, said last mentioned circuits each including the line conductor opposite that to which the substation relay is connected, and message registers controlled by said test relays.

7. In a telephone system, a party line, a central otfice, a relay at one substation of said line connectible to the tip conductor and operating to close a test circuit including the ring conductor, a relay at another substation connectible to the ring conductor. and operable to close a test circuit including the tip conductor, marginal test relays at the central oflice, means for including said marginal relays both in the operating circuits of the substation relays and in said test circuits, and message registers selectively operated. by said marginal relays.

8. In a telephone system, a party line, re-

lays, one at each of two substations on said line, unidirectional devices, one associated with each relay, the device at one of said substations permitting current of one polarity to flow through the relay and the device at the other substation permitting current of opposite polarity to flow through the associated relay, operating circuits for said relays including sources of potential and the conductors of said line, and means controlled by the relays for discriminating one substation from another.

9. In a telephone system, a party line, re; lays,'one at each of two substations on said line, unidirectional space discharge devices, one connected in series w1th each of said relays, the device at one of said substations permitting current of one polarity to flow through the relay and the device at the other substation permitting current of the opposite polarity to flow through the associated relay, operating circuits for said relays including the conductors of said line, sources of potential of different polarity for connection in said circuits, circuits closed by said relays in operating including the line conductors, and relays responsive to the closure of said last mentioned circuits for discriminating one substations or in response to unstandard conditions, on the line, message registers, an alarm device, circuits closed bysaid test relays when actuated in response to the substation relays for operating said registers, and

circuits closed by the test relaysiwhen operated in response to an unstandard condition on the line for actuating said alarm device. In witness whereof, I hereunto subscribe my name this 1 day of August, A. D. 1927.

' RAY L. STOKELY. 

